Various micro-electro-mechanical (MEM) devices, also known as micro-electro-mechanical systems (MEMS) devices, require the formation of a moving structure, e.g., a silicon structure. These structures have been formed using various techniques, including single crystal silicon and thin film surface micromachining. In general, surface micromachining requires the selective removal of a sacrificial film, to allow the MEM structure to move. In other MEM devices, a deep reactive ion etch (DRIE) has been utilized to form silicon structures, by etching through a silicon layer and stopping on a sacrificial oxide layer that is subsequently removed. In general, this process results in a high-aspect ratio silicon structure with relatively low stress. However, the process requires expensive silicon-on-insulator (SOI) wafers or non-standard thick polysilicon processes.
In some conventional approaches, utilizing a DRIE on an SOI wafer has resulted in an artifact at the oxide-silicon interface, due to charging of the oxide. This artifact (or footer) is generally undesirable. Designers have spent considerable effort to eliminate the footers that result from conventional processes.
What is needed is a technique for manufacturing a micro-electro-mechanical (MEM) structure that eliminates the need for the utilization of silicon-on-insulator (SOI) wafers or thick polysilicon wafers for forming single crystal silicon structures in a MEM device.